The Baltimore and Potomic Tunnel near Falls Road and the North Avenue Bridge. Replacing the tunnel could displace dozens of homes and subject hundreds more to noise and vibration during and after construction, a new study says.

The Baltimore and Potomic Tunnel near Falls Road and the North Avenue Bridge. Replacing the tunnel could displace dozens of homes and subject hundreds more to noise and vibration during and after construction, a new study says.

The Federal Railroad Administration has determined the most environmentally friendly option for replacing the 144-year-old Baltimore and Potomac Tunnel under West Baltimore — which currently acts as a bottleneck for Amtrak and other commercial rail traffic along the economically vital Northeast Corridor — is boring four new single-track tunnels deep below the city, to the tune of $4.52 billion.

No funding source has been identified. Still, the conclusion of the three-year, federally funded engineering and environmental study — announced Friday — was a necessary step before any large-scale project to replace the Amtrak-owned tunnel could get underway, and pushes the proposed project one step closer to reality.

If completed, the new tunnel would displace some homeowners, businesses and churches in West Baltimore, though officials said they attempted to mitigate such effects.

Replacing the tunnel, which is between the West Baltimore MARC station and Penn Station, has been a priority for Amtrak for years. While it is considered safe, it's unreliable, requires frequent maintenance and slows traffic along the nation's busiest rail corridor on a daily basis.

The new tunnel system would eliminate the current tunnel's sharp curves and allow Amtrak and MARC trains to travel at higher speeds under the city. It also would ease movement of commercial freight along the line, though the limitations of the existing tunnel already have pushed freight companies to find alternate routes through the region.

Federal officials say the replacement of the tunnel will "promote the long-term economic success of the city and surrounding region."

The selected replacement option would create a 3.67-mile stretch of rail that sweeps in a high west-to-east arc from the MARC station to Penn Station.

It would include a new rail bridge over Mulberry and Franklin Street and an open-cut section that transitions into a southern tunnel portal west of Payson Street between Riggs Avenue and Mosher Street. From the southern portal, a two-mile tunnel would be bored to the northern portal just east of Interstate 83.

It calls for three ventilation facilities — one at each of the portals, and one in the 900 block of W. North Ave.

The plan would require 22 residential buildings to be demolished, 15 of which are now occupied. It would displace 13 businesses in the Bridgeview/Greenlawn, Midtown-Edmondson and Reservoir Hill neighborhoods, including six near the south portal and seven at the location of the ventilation facility on North Avenue. Four places of worship in Midtown-Edmondson also would be displaced.

The report acknowledges that the plan "will have disproportionately high and adverse effects" in low-income and minority communities.

Officials said the study "established numerous mitigation strategies to minimize the project's impacts on surrounding communities, both during construction and after the new tunnels are operational." Officials said they are committed to ongoing public outreach as the search for project funding begins.

The study was conducted in consultation with city and state transportation officials, and included public comment periods.

Rail officials say the project is necessary because of the deteriorating condition of the existing tunnel and also because of the increasing demands of a growing regional population.

"As population increases and dependency on rail transportation grows," the FRA wrote in the report, "the demand for more efficient, better rail service within the Northeast megaregion is expected to rise."